I-Ethernet ikhona yonke indawo, futhi amashumi ezinkulungwane zabakhiqizi bakhiqiza imishini eyisekelayo. Kodwa-ke, cishe wonke lawa madivayisi anento eyodwa afanayo - :
$ ip l
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP
link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
I-MTU (Iyunithi Yokudlulisa Okuphezulu) ichaza usayizi omkhulu wephakethe ledatha elilodwa. Ngokuvamile, lapho ushintsha imilayezo ngamadivayisi aku-LAN yakho, i-MTU izoba ngohlelo lwamabhayithi angu-1500, futhi cishe yonke i-inthanethi isebenza ngamabhayithi angu-1500. Nokho, lokhu akusho ukuthi lobu buchwepheshe bokuxhumana abukwazi ukudlulisa osayizi bephakethe abakhulu.
Isibonelo, i-802.11 (eyaziwa kakhulu ngokuthi i-WiFi) ine-MTU yamabhayithi angu-2304, futhi uma inethiwekhi yakho isebenzisa i-FDDI, kusho ukuthi i-MTU yakho ingamabhayithi angu-4352. I-Ethernet ngokwayo inomqondo othi "amafreyimu amakhulu", lapho i-MTU inganikezwa usayizi ofika ku-9000 bytes (ngokusekelwa kwale modi ngama-NIC, ama-switch kanye nama-routers).
Nokho, kuyi-Internet lokhu akudingekile ikakhulukazi. Njengoba izisekelo eziyinhloko ze-inthanethi zakhiwe ngokuxhunywa kwe-Ethernet, usayizi wephakethe we-de facto ongekho emthethweni usethelwe ku-1500B ukugwema ukuhlukana kwephakethe kwamanye amadivaysi.
Inombolo engu-1500 ngokwayo iyamangaza - umuntu angalindela ukuthi ama-constants emhlabeni wekhompyutha asekelwe emandleni amabili, isibonelo. Ngakho-ke i-1500B ivelaphi futhi kungani sisayisebenzisa?
Inombolo yomlingo
Impumelelo yokuqala enkulu ye-Ethernet emhlabeni yeza ngendlela yamazinga. (mncane) futhi (ugqinsi), izinombolo ezikhombisa ukuthi ingxenye yenethiwekhi ethile ingamboza amakhulu amamitha amangaki.
Njengoba kwakunezivumelwano eziningi ezincintisanayo ngaleso sikhathi, futhi ihadiwe yayinemikhawulo yayo, umdali wefomethi uyavuma ukuthi izidingo zenkumbulo zephakeji lebhafa zabamba iqhaza ekuveleni kwenombolo yomlingo 1500:
Uma ubheka emuva, kuyacaca ukuthi ubukhulu obukhudlwana bekungaba yisixazululo esingcono, kepha ukube besinyuse izindleko zama-NIC kusenesikhathi, bekuzovimbela i-Ethernet ukuthi isabalale.
Nokho, lena akuyona yonke indaba. IN "I-Ethernet: Ukushintsha Kwephakethe Elisabalalisiwe Kunethiwekhi Yekhompyutha Yasekhaya," ngo-1980, ihlinzeka ngokuhlaziywa kwasekuqaleni kokuphumelela kokusebenzisa amaphakethe amakhulu kumanethiwekhi. Ngaleso sikhathi, lokhu kwakubaluleke kakhulu kumanethiwekhi e-Ethernet, ngoba ayekwazi ukuxhuma wonke amasistimu ngentambo eyodwa ye-coaxial, noma ahlanganise ama-hubs akwazi ukuthumela iphakethe elilodwa kuwo wonke ama-node engxenyeni efanayo ngesikhathi esisodwa.
Kwakudingeka ukukhetha inombolo engeke ibangele ukubambezeleka okuphezulu kakhulu lapho uthumela imilayezo ngamasegimenti (ngezinye izikhathi kumatasatasa), futhi ngesikhathi esifanayo ngeke kwenyuse inani lamaphakethe kakhulu.
Ngokusobala, onjiniyela ngaleso sikhathi bakhetha inombolo engu-1500 B (cishe amabhithi ayi-12000) njengenketho βephephileβ kakhulu.
Kusukela lapho, amanye amasistimu emiyalezo ahlukene afikile futhi ahamba, kodwa phakathi kwawo, i-Ethernet yayinenani eliphansi le-MTU namabhayithi ayo angu-1500. Ukweqa inani elincane le-MTU kunethiwekhi kusho ukubangela ukuhlukana kwephakethe noma ukuhileleka ku-PMTUD [ukuthola ubukhulu bosayizi wephakethe. endleleni ekhethiwe]. Zombili izinketho zazinezinkinga zazo ezikhethekile. Ngisho noma ngezinye izikhathi abakhiqizi abakhulu be-OS behlisa inani le-MTU eliphansi nakakhulu.
Ukusebenza kahle Factor
Manje sesiyazi ukuthi i-inthanethi ye-MTU ikhawulelwe ku-1500B, ikakhulukazi ngenxa yamamethrikhi okubambezeleka kwefa kanye nemikhawulo yehadiwe. Ngabe lokhu kuthinta kangakanani ukusebenza kahle kwe-inthanethi?
Uma sibheka idatha evela endaweni enkulu yokushintshanisa i-inthanethi ye-AMS-IX, sibona ukuthi okungenani ama-20% amaphakethe adlulisiwe anosayizi omkhulu. Ungabheka futhi inani lethrafikhi ye-LAN:
Uma uhlanganisa womabili amagrafu, uthola okuthile okufana nalokhu okulandelayo (izilinganiso zethrafikhi zobubanzi besayizi yephakethe ngalinye):
Noma, uma sibheka ithrafikhi yazo zonke lezi zihloko nolunye ulwazi lwesevisi, sithola igrafu efanayo enesilinganiso esihlukile:
Ingxenye enkulu yomkhawulokudonsa ichithwa kumaheda amaphakethe ekilasi likasayizi omkhulu. Njengoba i-overhead ephakeme kuthrafikhi ephakeme ingu-246 GB/s, kungacatshangwa ukuthi ukube sonke sishintshele "kuzimele we-jumbo" lapho inketho enjalo isesekhona, le nhloko ingaba ngu-41 GB/s kuphela.
Kodwa ngicabanga ukuthi namuhla ingxenye enkulu ye-Inthanethi leso sitimela sesivele sihambile. Futhi nakuba abanye abahlinzeki besebenza ne-MTU ye-9000, iningi aliyisekeli, futhi ukuzama ukuguqula okuthile emhlabeni jikelele ku-inthanethi kubonakale kunzima kakhulu ngokuphindaphindiwe.
Source: www.habr.com